Here is the situation. Small town police department wants to have some wireless access for their cruisers. They want to make a deal with the local McDonlands's to allow them to put their wireless antenna on their building (close to the highest in elevation in town)

The city will pay for a broadband account at the McD's
They want a 5 mile radius range.

First question:
What exactly is this
Seems to me that it is an access point that has the ability to connect to an outdoor antenna. Could I use this in conjunction with a inexpensive broadband router, and an omni directional antenna like this to do the job?

Or is there something better out there?
Is HomeRF worth considering, or is it dead compared to Wi-fi?
The more I read about this stuff the more confusing it gets.